Negative pressure-assisted porous structure with gradient dielectrics design for linearity enhancement of flexible capacitance pressure sensor

The trade-off between sensitivity and linearity range for flexible capacitive pressure sensors remains unresolved. Herein, a simple and low-cost method is proposed to fabricate porous structure with the aid of negative pressure. The gradient dielectrics are assembled with porous structure doped with different CNT ratios. With the perforated design on the low dielectric layer, the gradient dielectric can realize series-parallel conversion during the pressure-induced deformation process, where the coverage ratio and dielectric properties of low dielectric layer can be appropriately collocated to realize the linear behavior of the capacitance performance over the full-scale pressure. Therefore, the capacitive sensor based on optimized gradient dielectric layer can achieve a high sensitivity of 0.247 kPa−1 and a wide linearity range of 0–175 kPa. With the high sensitivity over a broad pressure range, the capacitive sensor demonstrates its various practical applications in monitoring physiological signals and human motions such as the artery pulse, respiratory, knee bending, elbow bending degree and walking and running status, showing potential in wearable healthcare monitor.